1. Field of the Invention
The present invention relates to novel polymer alloys comprising an ethylene-vinyl alcohol (EVOH) copolymer and a polypropylene (PP) and to the use of such novel alloys for the production of shaped articles having gas permeability properties and mechanical properties as to be suitable as packaging materials, for example monolayer or multilayer films, tubs, storage containers and the like.
The subject novel alloys are easily shaped employing techniques well known to this art, for example: extrusion coating, blow-extrusion, coextrusion, thermoforming, orientation and others.
2. Description of the Prior
The known packaging materials requiring very low gas permeability are produced from polymers having significant gas barrier properties.
Thus, EVOH is known to the art as an excellent barrier material from this standpoint, however, such copolymer presents a certain number of disadvantages, including its low processibility at high temperatures when compared with thermoplastic polymers such as polyethylene and polypropylene, typically employed in the field of packaging. It also has a rigidity and brittleness in the solid state which are such that, for example, when converted into film form, its gas permeability is not maintained when the film is subjected to repeated flexing, and cracking is a common result. In addition, its low processibility does not permit the material to withstand changes in geometry which are the usual in the processing of thermoplastics, such as orientation or thermoforming.